TO determine the mass of the helium in the balloon, we make use of the density of the gas that is given in the problem and the volume of helium that is present. Density is a property of a
material which describes the mass of a material per unit volume. By multiplying the volume to density, we get the mass of the helium gas in the balloon. We do as follows:
Mass = Density x Volume
Mass = 0.1785 kg / m^3 x 3249 m^3
Mass = 579.9465 kg
Therefore, the mass of helium gas in the hot air balloon would be about 579.9 kg.